This invention relates to the preparation of sterile medical articles by producing a chlorinated polymer that contains a metal complex, fabricating the medical article from the chlorinated polymer and exposing the medical article to gamma radiation. In particular, the metal complex used has at least one anionic ligand that has the least one resonance structure in which the charge is localized on a carbon atom.
Poly(vinyl chloride) (PVC) has properties that make it desirable for use as medical devices and as packaging for medical applications. Articles that are used in the medical field have to be sterilized before they are used. Gamma radiation is often used for this purpose. It has been found, however, that gamma radiation causes PVC to become yellow and medical articles that have turned yellow may be rejected as being of inferior quality. Articles made of PVC that are re-used and sterilized after each use are especially likely to turn yellow.
A variety of substances have been added to PVC to stabilize it from gamma radiation and prevent yellowing, including organic Ca.backslash.Zn soap blends (JP 57,003,653), organo tin compounds (JP 02189352, JP 08073619, and EP 83112278), and sulfur compounds (JP 08151495, 07102142, and 01278551).